1. Technical Field
The present invention relates to active-matrix circuit boards including drive electrodes and wiring patterns and displays including the active-matrix circuit boards.
2. Related Art
A variety of display panels (displays) including electrooptical devices have recently been put to widespread use. Accordingly, studies have also been directed to the use of such display panels as display units of, for example, clocks and various instruments.
These display panels (displays) require, for example, through-holes through which pointers are attached to indicate time when used as display units of clocks or to indicate scales (numbers) when used as display units of various instruments. An example of a display panel having a through-hole is disclosed in JP-A-2001-75112, which proposes a liquid crystal display panel designed for STN liquid crystal which operates by passive-matrix driving.
There is a demand for the application of active-matrix driving, rather than passive-matrix driving, to display panels (displays) used in devices such as clocks so that the devices not only can simply display numbers such as time, but also can display calendar information, including dates and days, and other various built-in functions (including a timer function, a stopwatch function, and a radio reception function).
To apply active-matrix driving, however, wiring lines such as data lines and scan lines must be arranged in a matrix. If a through-hole is formed in an active-matrix circuit board used as a component of a display panel by, for example, drilling, as described above, the data lines and the scan lines are impaired at a position where the hole is formed. If the active-matrix circuit board is used in a display panel having a rectangular screen, for example, no display is provided in a cross region including the through-hole, that is, in a display region including pixel electrodes connected to wiring lines designed so as to extend through the through-hole. For a matrix display having a through-hole, therefore, wiring lines designed so as to extend through the through-hole are required to extend around the through-hole with portions of the wiring lines near the through-hole bypassing the through-hole.
The liquid crystal display panel disclosed in JP-A-2001-75112 above has a through-hole in its display region so that an analog indicating instrument can be used in combination. X and Y electrodes arranged around the through-hole include electrode portions arc-shaped about the axis of the through-hole with predetermined curvatures. This liquid crystal display panel can effectively utilize the space around the through-hole to allow dense wiring and a specific display around the through-hole. This publication, however, makes no consideration of active-matrix driving with a thin-film transistor (TFT) panel and thus cannot meet the demand for the application of active-matrix driving.
For high-definition active-matrix displays, as described above, wiring lines such as data lines (signal lines) and scan lines (scanning lines) are required to extend around and bypass a through-hole. If the wiring lines are arranged so as to bypass the through-hole, however, pixel-driving circuits for driving pixel electrodes cannot be arranged at positions where the wiring lines are formed. For high-definition displays, particularly, numerous wiring lines must be arranged so as to bypass the through-hole, and the regions where the pixel-driving circuits are formed are limited accordingly. As a result, the total display area is decreased because no display can be provided around the through-hole.
One possible approach to this problem is to allow sufficient space for the placement of the pixel-driving circuits, that is, to ensure sufficient spaces between the pixel-driving circuits, by lowering definition so that the wiring lines can extend through the spaces.
Another possible approach is to ensure a sufficient region where the pixel-driving circuits are formed near the through-hole by increasing the number of layers where the wiring lines are formed and forming the wiring lines in different layers so that the wiring lines do not interfere with each other. This allows the pixel electrodes for display to be provided near the through-hole.
The approach of lowering definition, however, decreases display quality and thus cannot provide a sufficiently valuable product even though the display region can be expanded to the vicinity of the through-hole and a larger display area is ensured thereby.
Also, the approach of increasing the number of layers where the wiring lines are formed correspondingly increases the number of manufacturing steps and thus significantly increases manufacturing costs.